1. Field of the Invention
The present invention relates to a hologram recording material suitable for volume hologram recording, and a hologram recording medium having a hologram recording layer made of the hologram recording material.
2. Disclosure of the Related Art
Research and development of holographic memories have been advanced as recording technique making it possible to attain large-capacity recording and high-speed data transmission. Examples of the property required for a hologram recording material include high refractive index change at the time of recording, high sensitivity, low scattering, environment resistance, that is, storage stability, durability, low dimension change, high multiplicity, and the like.
As a hologram recording material, attention has been paid to an organic-inorganic hybrid material, which is made mainly of an inorganic matrix and a photopolymerizable monomer, and the hybrid material has been investigated. The inorganic matrix is excellent in environment resistance and durability.
For example, Japanese Patent No. 2953200 (Patent Document 1) discloses an optical recording film wherein a photopolymerizable monomer or oligomer and a photopolymerization initiator are contained in an inorganic substance network film. As the photopolymerizable monomer, disclosed is a monofunctional (meth)acrylic acid ester, a polyfunctional (meth)acrylic acid ester, or the like (paragraph [0017]).
JP-A-11-344917 (Patent Document 2) discloses an optical recording medium wherein an organic-inorganic hybrid matrix contains therein a photoactive monomer. As the photoactive monomer, disclosed is an acrylic acid ester monomer such as diethylene glycol monoethyl ether acrylate (paragraph [0018]).
JP-A-2002-236439 (Patent Document 3) discloses a hologram recording material comprising: a matrix made of an organic-inorganic hybrid polymer obtained by copolymerizing an organometallic compound containing an ethylenically unsaturated double bond and an organic monomer having an ethylenically unsaturated double bond, as main chain constituting components, and/or a hydrolytic polycondensate thereof; a photopolymerizable compound; and a photopolymerization initiator. As the photopolymerizable compound, a radical photopolymerizable compound or a cation photopolymerizable compound is described (paragraph [0041]); and as the radical photopolymerizable compound, a (meth)acrylic acid ester monomer is disclosed (paragraphs [0042] to [0043]).
JP-A-2005-77740 (Patent Document 4) discloses a hologram recording material comprising metal oxide particles, a polymerizable monomer, and a photopolymerization initiator. As the polymerizable monomer, a (meth)acrylic acid ester monomer is disclosed (paragraph [0020]).
JP-A-2005-99612 (Patent Document 5) discloses a hologram recording material comprising a compound having one or more polymerizable functional groups, a photopolymerization initiator, and colloidal silica particles. As one species of the polymerizable functional groups, an acrylic acid ester monomer is disclosed (paragraphs [0019] to [0022]). As a different example thereof, an acrylamide (for example, ethylenebisacrylamide) is disclosed (paragraph [0023]).
JP-A-2005-321674 (Patent Document 6) discloses a hologram recording material comprising: an organometallic compound at least containing at least two kinds of metals (Si and Ti), oxygen, and an aromatic group, and having an organometallic unit wherein two aromatic groups are directly bonded to one metal (Si); and a photopolymerizable compound. As the photopolymerizable compound, a radical polymerizable compound or a cation polymerizable compound is described (paragraph [0039]); and as the radical polymerizable compound, a (meth)acrylic acid ester is disclosed (paragraph [0041]).    Patent Document 1: Japanese Patent No. 2953200    Patent Document 2: JP-A-11-344917    Patent Document 3: JP-A-2002-236439    Patent Document 4: JP-A-2005-77740    Patent Document 5: JP-A-2005-99612    Patent Document 6: JP-A-2005-321674    Patent Document 7: JP-A-2006-225446